1. Field of the Invention
This invention relates to semiconductor device packaging technology, and more particularly, to a method of underfilling a flip-chip semiconductor device.
2. Description of Related Art
FIG. 1A shows a flip-chip semiconductor package which utilizes a conventional flip-chip underfill method. As shown, this package includes a semiconductor chip 1 whose circuit surface 11 (the side where active semiconductor and circuit elements are formed) is provided with a plurality of solder bumps 6. Through reflow treatment, the circuit surface 11 of the chip 1 is bonded and electrically coupled to the top surface 31 of a substrate 3. After this treatment, a gap 5 is left between the circuit surface 11 of the chip 1 and the top surface 31 of the substrate 3. It is required to perform a flip-chip underfill process to fill up this gap 5 with resin for the purpose of increasing the solder joint between the solder bumps 6 and the substrate 3 and preventing the solder bumps 6 from being damaged. A conventional method for this purpose is to use a dispensing needle 2 and place the outlet of the dispensing needle 2 beside the chip 1 at a position below the circuit surface 11 of the chip 1 and above the top surface 31 of the substrate 3. The injected resin will then spread out over the top surface 31 of the substrate 3 and fill into the gap 5 through capillary action until the gap 5 is entirely filled with the resin.
One drawback to the forgoing flip-chip underfill method, however, is that the injected resin from the dispensing needle 2 would spread randomly over the top surface 31 of the substrate 3, making some portions of the resin flash to other surface part beyond the gap 5. As a result, a cleaning process is required after the flip-chip underfill method is completed, which would increase the overall manufacture cost.
Still one drawback is that the foregoing flip-chip underfill method is unsuitable for use on a stacked type of flip-chip package configuration, such the one shown in FIG. 1B. As show, this package configuration includes two chips: a first chip 9 and a second chip 1. The first chip 9 is wire bonded to a set of gold wires 90 for electrically coupling to substrate, while the second chip 1 is bonded and electrically coupled to the first chip 9 through a plurality of solder bumps. In this case, the dispensing needle 2 would be obstructed by the gold wires 90 from lowering to a suitable position where resin injection can be made.
Moreover, the foregoing flip-chip underfill method is also unsuitable for use on a package configuration with passive components such as the one shown in FIG. 1C. As shown, this package configuration includes a semiconductor chip 1 and a plurality of passive components 32 mounted on the top surface 31 of a substrate 3. In this case, the dispensing needle 2 would be obstructed by the passive components 32 from lowering to a suitable position where resin injection can be made.
The U.S. Pat. No. 5,942,798 entitled xe2x80x9cAPPARATUS AND METHOD FOR AUTOMATING THE UNDERFILL OF FLIP-CHIP DEVICESxe2x80x9d discloses an advanced flip-chip underfill technique, which is briefly described in the following with reference to FIG. 2. As shown, this patented flip-chip underfill technology is utilized on a package configuration having a semiconductor chip 1 mounted in a flip-chip manner on a substrate 3, and is characterized in the forming of an underfill dam 7 beside the chip 1 for preventing the injected resin from the dispensing needle 2 from spreading to other areas beyond the intended area. One drawback to this patented technology, however, is that the forming of the underfill dam 7 requires additional layout areas over the substrate 3, and thus would make the overall package configuration less compact.
The U.S. Pat. No. 5,710,071 entitled xe2x80x9cPROCESS FOR UNDERFILLING A FLIP-CHIP SEMICONDUCTOR DEVICExe2x80x9d discloses another flip-chip underfill technique, which is briefly described in the following with reference to FIG. 3.
As shown, this patented flip-chip underfill technology is utilized on a package configuration having a semiconductor chip 1 mounted in a flip-chip manner on a substrate 3, and is characterized in the forming of an opening 8 in the substrate 3 at a position directly beneath the center of the chip 1. This opening 8 allows the air in the gap 5 to be substantially entirely dispelled out therethrough by the injected resin from the dispensing needle 2, so that the filled resin beneath the chip 1 would be substantially free of voids. One drawback to this patented technology, however, is that it requires the dispensing needle 2 to move around the chip 1 in order to inject resin around the chip 1, and therefore, in the case that gold wires or passive components are mounted beside the chip 1, the dispensing needle 2 would be obstructed from entering these positions.
It is therefore an objective of this invention to provide a method for underfilling a flip-chip semiconductor device, by which the resin injection would be unobstructed by gold wires or passive components beside the flipped chip.
It is another objective of this invention to provide a method for underfilling a flip-chip semiconductor device, which allows the injected resin to be confined to the intended area so that no resin would be wasted.
In accordance with the foregoing and other objectives, the invention proposes a new flip-chip underfill method.
In one embodiment, the flip-chip underfill method of the invention comprises the following procedural steps: preparing a substrate having a front surface and a back surface; preparing a semiconductor chip having an active surface and an inactive surface; providing a plurality of solder bumps on the active surface of the semiconductor chip; mounting the semiconductor chip in a flip-chip manner over the front surface of the substrate, which forms a gap between the active. surface of the semiconductor chip and the top surface of the substrate; and moving a dispensing needle having an outlet in such a manner as to position the the outlet of the dispensing needle at a corner point between the inactive surface and the sidewall of the semiconductor chip, allowing injected resin from the outlet of the dispensing needle to flow down along the sidewall of the semiconductor chip to the edge of the active surface of the semiconductor chip and subsequently fill into the gap through capillary action.
In another embodiment, the flip-chip underfill method of the invention comprises the following procedural steps: preparing a substrate having a front surface and a back surface; preparing a first semiconductor chip having an active surface and an inactive surface; preparing a second semiconductor chip having an active surface and an inactive surface; mounting the second semiconductor chip on the front surface of the substrate; providing a plurality of solder bumps on the active surface of the first semiconductor chip; mounting the first semiconductor chip in a flip-chip manner over the active surface of the second semiconductor, which forms a gap between the active surface of the first semiconductor chip and the active surface of the second semiconductor chip; moving a dispensing needle having an outlet in such a manner as to position the outlet of the dispensing needle at a corner point between the inactive surface and the: sidewall of the first semiconductor chip, allowing injected resin from the outlet of the dispensing needle to flow down along the sidewall of the first semiconductor chip to the edge of the active surface of the first semiconductor chip and subsequently fill into the gap through capillary action.
Fundamentally speaking, the flip-chip underfill method of the invention can be utilized for underfilling a gap formed beneath a semiconductor chip mounted in a flip-chip manner over an underlying surface, and comprises the steps of preparing a dispensing needle having an outlet; moving the dispensing needle in such a manner as to position the outlet thereof at a corner point between the upper surface and the sidewall of the semiconductor chip; and injecting resin at the targeted corner point, which allows injected resin from the outlet of the dispensing needle to flow down along the sidewall of the semiconductor chip to the edge of a lower surface of the semiconductor chip and subsequently fill into the gap through capillary action.
The flip-chip underfill method of the invention is more advantageous to use than the prior art since it allows the dispensing needle to be unobstructed by the gold wires and also allows the injected resin to be substantially confined to the targeted area without being wasted.